Statistical analysis

Statistical analyses were carried out using spss (version 18.0; IBM Corporation, Armonk, NY, USA) and open‐source R (version 2.15.1; Auckland University, Auckland, New Zealand) software. Data were plotted with Graph Pad Prism software (version 5.0; GraphPad Software; La Jolla, CA, USA). Continuous variables are presented as the mean ± standard deviation; the t‐test was used for comparison between two groups, and the F‐test (analysis of variance) was used for comparison of groups of more than two. Categorical variables were expressed as percentages. The χ²‐test was used for comparison between multiple groups. A P‐value <0.05 was considered statistically significant.

The receiver operating characteristic (ROC) curves were achieved using open‐source R software (version 2.15.1; Auckland University) and the p‐ROC package²³. In the present study, two ROC curves were plotted: one for people diagnosed with diabetes, and the other for people diagnosed with prediabetes by FPG, 2 h‐PPG and HbA1c, respectively. In general, an area under the curve (AUC) >0.9 indicates a high diagnostic value, 0.7 < AUC ≤ 0.9 indicates a moderate diagnostic value, and 0.5 < AUC ≤ 0.7 indicates a low diagnostic value. Optimal cut‐off values were obtained based on the highest Youden index across various cut‐off points as reviewed previously²⁴.